The present invention relates to a master cylinder for supplying brake fluid to a brake apparatus.
The master cylinder of the above-mentioned type comprises, for example, a cylinder body 81, a reservoir 82 and seal members 83 as shown in FIG. 9. The cylinder body 81 is connected to an input member, such as a brake pedal, so as to supply a brake fluid to a brake apparatus (not shown) in a volume corresponding to an input from the input member. The reservoir 82 stores the brake fluid. The brake fluid in the reservoir 82 is supplied to a cylinder bore (not shown) in the cylinder body 81, if desired. When the reservoir 82 is mounted on the cylinder body 81, the seal member 83 seals a gap therebetween. Two cylindrical mount portions 84 are formed at an upper portion of the cylinder body 81 so as to communicate with the cylinder bore through passages. The reservoir 82 is mounted on the cylinder body 81 by attaching the cylindrical seal members 83 to respective inner circumferential surfaces of the mount portions 84 and fitting cylindrical leg portions 85 of the reservoir 82 into the seal members 83. In this state, the cylinder bore in the cylinder body 81 and the reservoir 82 are communicated with each other. As shown in FIG. 10, a mount opening 86 is formed in the mount portion 84 of the cylinder body 81, and a claw portion 87 extends radially inward from an inner circumferential surface of a distal end of the mount opening 86. The cylindrical seal member 83, which includes a stepped portion on an outer circumferential surface thereof, is inserted from the distal end of the mount opening 86 and retained in the mount opening 86. The seal member 83 comprises a first annular portion 88, a second annular portion 89 and a third annular portion 90 continuously and coaxially arranged in an axial direction of the seal member 83. The first annular portion 88 has an outer diameter larger than an inner diameter of the claw portion 87. The second annular portion 89 has an outer diameter smaller than the outer diameter of the first annular portion 88 and has an outer circumferential surface facing an inner circumferential surface of the claw portion 87. The third annular portion 90 has an outer diameter larger than the outer diameter of the second annular portion 89 and has an outer circumferential surface facing an inner circumferential surface of the mount opening 86 on a proximal side thereof relative to the claw portion 87. A flange portion 91 extends radially outward from an outer circumferential surface of a distal end portion of the leg portion 85.
An engaging surface 92 of the flange portion 91 of the reservoir 82 on a side of the seal member 83 and an engaging surface 93 of the claw portion 87 of the cylinder body 81 on a side the seal member 83 engage with each other through the seal member 83, so as to prevent separation of the reservoir 82 from the cylinder body 81 and the seal member 83.
However, when the engaging surface 92 of the flange portion 91 and the engaging surface 93 of the claw portion 87 are indirectly engaged with each other through the seal member 83, retention of the reservoir 82 relative to the cylinder body 81 and the seal member 83 is not secured. In conducting vacuum filling of the brake fluid into brake piping, when the pressure of the brake fluid exceeds a predetermined level or when an external force is applied to the reservoir 82 during the time the vacuum filling is conducted, there is a possibility of separation of the reservoir 82 from the cylinder body 81.
To retain securely the reservoir relative to the cylinder body, it has been attempted to use conventional retaining mechanisms which have been employed in various techniques relating to the master cylinder. For example, the reservoir and the cylinder body have been further connected at a connecting portion other than the leg portion and the mount portion, and there has been provided a retaining pin which extends through the connecting portion. As another example, there has been provided a mechanism in which a projecting portion is formed in the cylinder body so as to project toward the reservoir and a portion having a fit with an intermediate part of the projecting portion is formed in the reservoir, and a retaining ring is externally attached to these portions when they are in a fitted state.
However, when conventional retaining mechanisms such as those mentioned above (external attachment of the retaining pin or retaining ring) are simply used for securely retaining the reservoir relative to the cylinder body, a connecting portion other than the leg portion and the mount portion must be formed, resulting in a master cylinder having a complicated structure. Further, a cumbersome operation is required for attachment of the retaining pin or retaining ring. As a result, the cost of the master cylinder substantially increases.
In view of the above, the present invention has been made. It is an object of the present invention to provide a master cylinder in which retention of the reservoir relative to the cylinder body and the seal member can be secured, without occurrence of a substantial increase in cost.
In order to achieve the above-mentioned object, the present invention provides a master cylinder comprising: a master cylinder body; a reservoir connected to the master cylinder body; a leg portion formed in the reservoir so as to protrude toward the master cylinder body; a mount portion formed in the master cylinder body so as to protrude toward the reservoir, the mount portion including an opening into which the leg portion is inserted; and a seal member adapted to be interposed between the leg portion and the mount portion when the leg portion is inserted into the opening of the mount portion, so as to seal a gap between the master cylinder body and the reservoir. The leg portion extends beyond the seal member and includes a flange portion formed along an outer circumference of a distal end thereof. The flange portion protrudes outward and includes an engaging surface facing the seal member. The seal member includes an engaging surface formed at an end portion thereof. The engaging surface of the seal member faces the flange portion. The master cylinder further comprises a retaining member adapted to be fitted on an outer circumferential surface of the leg portion. The retaining member is provided between the engaging surface of the flange portion and the engaging surface of the seal member so as to prevent separation of the reservoir from the master cylinder body.
In a preferred embodiment of the present invention, the retaining member has an outer diameter which is larger than an outer diameter of the flange portion and an inner diameter which is smaller than the outer diameter of the flange portion when the retaining member is provided between the engaging surface of the flange portion and the engaging surface of the seal member. By this arrangement, the reservoir is engaged with the retaining member having an outer diameter larger than the outer diameter of the reservoir flange portion. Consequently, retention of the reservoir relative to the cylinder body and the seal member can be strongly secured. Further, such a strong retention can be achieved at the connection between the leg portion and the mount portion which are provided for permitting communication between the reservoir and the cylinder body. Therefore, the structure of the master cylinder does not become complicated. Further, the retaining member can be interposed between the seal member and the reservoir flange portion by preliminarily disposing the retaining member within the opening of the mount portion of the cylinder body and attaching the seal member to the mount portion, followed by fitting the leg portion of the reservoir into the retaining member and the seal member by a single fitting operation. Therefore, the reservoir can be easily mounted on the cylinder body.
The foregoing and other objects, features and advantages of the present invention will be apparent from the following detailed description and appended claims taken in connection with the accompanying drawings.